Manufacture of evaporated milk



March 27, 1945. R. wHlTAKER ETAL y MANUFACTURE 'OF EYAPORATED MILK I Filed March s; 1941 gew S m ..R r wm m e W Nm. Nw R E .o v O Vdm T vNno. T WA 1 a e n kyfY Ma.. Y we@ Y n Y o m mx a. R

Patented Mar. 27,

UNITED 4s'ng'rlss Pli'rE'rsrrv OFFICE t: M A

mdtllwhltihenmmmm E. Bombes-iet, Bnl

MiLndgnonto '8ealtest,1no., Baltimore, Md.,aeorporationof' Applicando Maren 3,1m, sain n. :sus:

claim; (mss-+2,14)

This invention relates to improvements in the preparation oi' evaporated milk and relates more particularly to methods of concentrating, packaging and sterilizing evaporated milk in order t0 improve its appearance, physical characteristics and ilavor.

' Evaporated milk, as 'now produced cially, has a number of imdesirable characteristics which render it noncompetitive with fresh or pasteurized milk in many fields. It has been recognised that the present types of7 evaporated milk have an undesirable ilavor, variously described as "cooked or "caramelized. Moreover, such evaporated milk has a dark color which dis.- tlnguishes it from fresh or pasteur-ized milk and which is objectionable to many people. VAlso. commercially available evaporated milks cannot acoordanceuwithourinvention can be withrennet.

It is well knowmof course. that the cook "l or "caramelised" ilavor of evaporated milk results from the sterilization ofthe milk. Although this flavor is undesirable it has not been possible, v

with prior methods. vin sterilize the milk without the milk acquiring the cooked"l or "caramelized iiavor. v

' We have foimd that it is possibleto sterilize evaporated milk without imparting the "cooked" Y or "carumelilei iiavor to the x'nilk and, there-4 fore, another object oi' the invention is to provide evaporated milk in which the cooked or carameliagedfiavorisminimized orentirely eliminated.

Prior methods-of sterilixing evaporated milk abocausethemilktoturn'dark apparently for bccoagulatedwichrennetukerresncrpasteurised theforewarmingofthefreshmilktoatemperar' ture vabove 200 1". in order to stabilize the milk.

milkwithoutthe-abovementioned reactionbe- Itis thenwncentratedtothedesir'edtotalsolids or di-sodium phosphate to adJst the salt balance and regulate the viscosity of the milk. The concentrated milk is then illledinto suitable concontent, treated with sans such as sodium citrate as talnersandsterilized. Usually,themilkis.

sterililedbyheatlngtobetweenbutwllto 40 245 l'. for a period of between about 12 and 18 minutes although the sterilization may take place the reasonthat caramelintion is accomplished by a darkening ofncomponents of the milk.

We have found that discoloration of themilk canboavoicleiiduringsterilization-and,therefore, f

another obkct of the invention is to provide sterililed'evaporated milkwhichhas acolorsimilariofreshmilkandcream.

containers for evaporated milk always are dis-v eolored. It appears that the discoloration isdue toareactionbetweenthemetallicsurfacesof containerwsilandcertaincompoimds form in themilkbytheprolonged heating during sterilisation.

Wehavefoimdthatitispossibletosterilizethe tween the metallicwalls of thecontainer and compounds preaentintheheatedmilkbygreatly nducinthetimethatthemilkisheldattempentureswherethesereactionstakeplace.

A high sterilizing temperature and then quickly cooled without holding at the sterilizing temperature. It has been found that it is possible to de stroy resistant bacterial spores that may be present in the milk by subjecting them momentarily to very high temperature. that is, temperatures in the range of 260 to 275 .11'. by bringing the Vcontainers of milk into contact with a Vmedium having a temperature between' about 280 and 300 F., which is well above the highest temperature reached in thecenter o! the container. 'I'he more rapidly the temperature is raised to this critical sterilizing range and the faster the cooling, the less the iiavor of the milk changes. In order to accomplish this rapid heating the contents of the container must be agitated vigorously in such a manner that maximum heat transfer takes place.

Although various methods of agitating the cans may be employed, the rotation oi' the can in a horizontal position about its longitudinal axis hasbeen found to be the most eiIective. This is not only the most practical and economical means from the standpoint of the mechanical handling of the containers. but it is also advantageous because the centrifugal force developed by the whirling container causesintimate contact between the milk and the-inner surface of the container and eliminates bubbles or foam which seriously interfere with heat izansfer.

I'he seam on the inner surface of metal cans aids in agitation of the milk when the cans are rotated about their longitudinal axes.- Furthermore. the head space which exists in the form of' a gas bubble when the cans are in a horizontal'. position aids in the agitation or the contents. In carrying out this operation, the milk in con.- tact with the wall of the container at any instant is momentarily at a temperature near that of the'l .heating medium, and at this s for a ame, not exceeding 'about The forewarming treatment is anl terial spores are instantly killed.

Milk-processed bythe method of sterilization described above s several characteristics which distinguish it from milk processed by conventional methods of sterilization, in which the milk is heated at lower temperatures but vfor longer periods of time.

One of the chief characteristics of evaporated asrasso productonprolongedstorsseaiiavorbestdescribed asoxidized. Therefore, in with the present invention it is highly desirable to remove substantially alloftheongen from the container and the milk before sterilization. This maybe accomplished by protecting the evaporated milk from contact with air after it is drawn from the vacuum pan, atwhich time it is oxygen-free. Protection is afforded the evaporatedmilkbythenseoi closedtypeaofeiiuiP- ment which do not permit-entry of air. or by excluding the air by maintaining an atmosphere of inert gas in the equipment. Dairy products or water used for standardization of the evaporated miik are de-aerated to remove all oxygen.

As a further protective measure the milk is protected from reincorporation of oxygen from oir during the canning operation. This vmay be accomplished in any one of several ways or a comblnation of the several ways, for example, the

'air in the empty can being conveyed to the nller may be exhausted by a vacuum and replaced by product may be removed by introducing a suitan inert gas; theiilled cans may be evacuated andthe head space iilled with aninert or oxygen free gas; or the product maybe packed and 'sealed in the container under a vacuum.

Any oxygen in the sealed can the able quantity of metallic calcium in the form of a powder or fine iilings, immediately prior to sealing the can. which eectively removes `any oxygen due to the formation of, nascent hydrogen.

For better understanding of the present invention'reference can behad to-the accompanying drawing in which:

Fig. 1 is a diagrammatic showing of a typical l form of apparatus for preparing evaporated milk in accordance with the present invention; and

Fig. 2 is a view in longitudinal section of ,a

device for sterilizing the evaporated milk.

As shown in Fig. 1 of the drawing, a typical form of apparatus for preparing evaporated milk in accordance with the present inventionmay consist oi' a milk storage tank I from which milk is deliveredvbylpump! to a tube type of forewar'ming device I. The warmed milk then passes into the hot well I where the temperature is raised still further by means of a steam 'injector 15- minutes.

important factor in controlling the vviscosity that is developed inthe evaporated milk by the sterilizing process and therefore, is indirectly an immilksterilized according to this invention is thes iiavor. Because of the rapidity of heating there is little, ii any, of the caramelization which imparts vthe typical "cooked milk i'iavor andthe ,dark color to the products now on-the market.

When the sterilizing conditions are such that .caramelization occurs in evaporated mill:` cer-l tain vcompounds are formed which act asanti- 55 oxidants preventing oxidation of susceptible nv, stituents in the product during prolonged storage. At the same time, reactions occur which tion o! antioxidants and the removal of oxygen does not take place and there develops 'in this portant factorinpreventing fat separation in the sterilized product.l At the end of this time the I nilkl is withdrawn into the vacuum pan t while a vacuum is maintained in the latter and where the milk is evaporated. A vacuum is maintained on the vacuum pan 6 by means of the vacuum pump .thereby evaporating the liquid from the milk and removing oxygen therefrom. The condenser 1 condenses the vapor removed from the The evaporatedmilkl is then withdrawn from the vacuum pan-.6 by means of a pump 9 and .delivered to a 4holding tank l0 from which the milk is delivered to a homogenizer Il. The function of'the tank III is to, equalize the i'lowfof the y condensed milk to the homogenizer.

The milk then iiows from the homogenizer Il l vto a cooler Il, preferably of the plate or internal tube type. in which the milk is cooled. The milk passes from the cooler I! i to a condensed milk storage tank in which atmosphere of inert gas vli'le autoclavechamber 2l also has al 2,s72,2s9 .is maintained. suon'gas being supplied from a cylinder Il and the pressure in the storage tank being equaliaed by 'an escape valve I5. If desired,

the milk can be standardized at this ,stage by adding oxygen-free milk products or water.

'I'he milk 'if delivered from the storage tank I3 vto a can llr supply tank Ii in which a constant level. of milk is maintained by means of a float valve I'I. 'I'he milk ilows from the supply tank Iiiv toa can 'filler Il beneath which cans I9 are l delivered by means .of a, suitable conveyor 2l from a can supply conveyor Il. Before passing to the c an illler Il the cans are deaerated by passing them through a vacuum chamber 22 in which a vacuum is maintained by means of the vacuum pump 2l and then the cans are lled with inert gas. Moreover, before being lled with milk, the cans I 0, which may be of the conventional vent hole type, may be supplied with rnetallic calcium at a stage 2l which removes any of the cans. n will be understood thaw-.he steri- .lizerdescribed above may' be modiiled considerably and that other types of sterilizers, for ex- -ample, baths of high boiling temperature salt' solutions or organic liquids may be used,.in order to'qiiickly raise'the milk to sterilizing tempera# ture.

summarizing the operation of the apparatus described above and the preferred process as vpactioedwith this apparatus: The milk in tank I is raised to a forewarming temperature between 150 and 180 F., at which temperature it is maintained for a' period of between 5 and 15 minutes during passage through the fcrewarmer I 3 vandA the holding tank l. The forewarming time and temperature will vary depending upon the characteristics of the milk. The forewarmed milk residual oxygen' from the milk and container or an antioxidant maybe supplied to thevmilk.

After the"cans I9 have been lled at the can v illler'they pass to a sealing device 25 where the can is sealed and then may be suitably tested for leaks. As an additional precaution, the cans, immediately before sealing, may be subjected 'to a vacuum and inert gas injected into the head space of the cans. The above described elements of the device may be of any desired type and are, in practice, conventionalelements readily available on the market and well known in the art.

After the 'cans I9 are`tested, they'are passed vto a sterlllzer 20. Fig. 2 illustrates a forni of autoclave or pressure chamber which may-*be employed. The'autoclave consists of an autoclave or pressure chamber 21 in which is rotatably mounted ureell n having .a multiplicity of' perforations 28 therein. The reel may be suitably supported upon a shaft Il' which passes through the end wall 3| i the autoclave and' is 4driven by a motor, not shown. The autoclave 'Il has a door I2 thereon by means of which the autoclave may be sealed to withstand substantial internal pressure.-

In the bottom Vportion of the autoclave cham.v ber 21 is located a manifold 3l to which steam is supplied by .means of the pipe 3l. -Water and compressed air are supplied to the autoclave 21 by means of a pipe 30 having a valve 31 therein.

`outlet 38 and a. valved drainage outlet 30 'for condensate therein. In the center of the reel is a compartment in which the cans I! are re- .oelved so that the oms -ls maybe roundabout their longitudinal axes during sterilization. Preferably the cans are rotated at about 100 to revolutions per minute. This high' speed rotation of thecans Il agitates thelnilk violently then passes vto the vacuum pan where vacuum evaporation of the milk is conducted at about 130 F., until the total solids content of the milk reaches about 26%. 'I'he milk is then homogenized to render it uniform, cooled in the cooler Iland delivered to the holding tank I3 where it is maintained under an atmosphere of inert gas. Thus, during the evaporation, homogenization, cooling and storage, the milk is maintained out of contact with and free from oxygen.

The milk is then delivered to the .can lling machine II where it is filled lntoecrans which previously have been de-aerated and-filled with inert gas. Metallic calcium ma be placed in the can in order to .react with sidual oxygen from the milk. i The cans are then sealed, tested for leakage and sterilized. If desired, the milk may be heated to a temperaturev its initial temperature to a temperature of between 260" and 275 F. measured at the center of a standard 14% ounce can in a period not' blow-off andcauscsarapidreplacel'neutoithemilklnl withV the. can walls,- thereby heating the milk to a high temperature but preventing it liner' 20 permits the temperature-of the milk in the cans to be raisedvery rapidly to theA desired' sterlll'aing temperature. I'he temperature of the from being maintained at this high temperature l for a. suilicient 'length the milk was about F., or in about 1% minutes if the'temperature of the milk in the cans was between 160 to 190' l". Upon attaining this sterllizing temperature, the milk is abruptly cooled by directing cold water. or other liquid into the sterllizer il. -The extremely short pef riod of heating, even at high temperatures sufv time, approximately one month, it is unnecessary cans can be reduced very abruptly. by shutting olf-the steam and supplying cold water and compressed airto thesteriliner 20 through the pipeA 30. 'Maintenance oflpressure in the sterilizer 20 during cooling'is desirable to'prevent distortion 'to store it at Vlorw temperature. inasmuch as it has been found that desirable savon in this short period of time. I above described operation producesa milk product which has novel namely, a fresh milk flavor, a white or creamy color, a high viscosity and other characteristics similar do `not develop to fresh milk, such 'as the ability to be coagulated with rennet and whipped like cream, if subjected to 'aheating andi chilling operation before whipping. Moreover, it lhas been found that the dJ remove the redark coloiation after the above treatment.

.From the foregoing description of a typical process embodying 'the invention and the resulting products, it will be apparent that milk prod` uctsV made in' accordance with the process have novel and highly desirable It will be understood, o1' conne. that the procecs described above may be varied widely, auch as for example, by combining one or more of the stepsoftheprocessandthatwidelyvaryingap-I containing evaporated milk about its longitudinal axis with said axis in a horinontal position `while subjecting the container to a heated uid at a temperature suiilcient to raise the temperature lPrimm: No. 2 572,259.

arance Vtionvrrhile subjectingthccontainertoaheated" CERTIFICATE oF common. v

RANDALL WIITAKER, ET` AL.

o! thcmilkto between about`260nnd 215' l'. inaperiodnotaboutZmhiutesand when saidmilkreach a temperature between ibout 260' and 275 F. immediately cooling the milkby brlllinsthe container into contact with ycoldlklllid- '2. A process for sterilizing evaporated milk which comprises filling evaporated milk into n container, preheating the milk in the container to atemperature between about 160' and 190' F., thereafter rotating said container about its longitudinalaxiswlthsaidaxisinahorimntalposifluid at a temperature mmcient to raise the temperature ofthe milk from between 160 and 190*- `Etobetweenli" andZIS'Rinaperiodnot about 1% minutes and when said milk attalnsatemperaturebetweensboutmand 275 immediately cooling the milk by bringing the container into contact with cold liquid.

man. warum.

nonm'r r. MYERS. nomi' n. no

man 27 1915.

' `It is hereb" certifiedthat error appeesr'grn the printed specification ofthe above numbered patentlrequiring correction aslfoll'one: Page 1, sec- I ond column, line 25, for "haz"l 'read -hae; page 5, second column, line 15 lfter the word 'between'I insert .'about'; line" 66, for' desirablez read undes1rab1e; yand that the seid Letter-s Patent ahouldbe read with ibis correction lherein that the eamo-nay 'conform to the record` of the case in eine Patent office.

signed and sealed this 5th day er June, l. n. '19h15.

`I (Seal) Leslie Frazer Acting Commissioner of Patents.

dark coloiation after the above treatment.

.From the foregoing description of a typical process embodying 'the invention and the resulting products, it will be apparent that milk prod` uctsV made in' accordance with the process have novel and highly desirable characteristi.

It will be understood, o1' conne. that the procecs described above may be varied widely, auch as for example, by combining one or more of the stepsoftheprocessandthatwidelyvaryingap-I containing evaporated milk about its longitudinal axis with said axis in a horiaoutal position `while subjecting the container to a heated uid at a temperature suiilcient to raise the temperatme lPrimm: No. 2 572,259.

avance Vtionvrrhile subjectingthccontainertoaheated" CERTIFICATE oF common. v

RANDALL WIITAKER, ET` AL.

o! thcmilkto between about`260nnd 215' l'. inaperiodnotexceedingaboutZmmutesand when saidmilkreaches a temperature between ibout 260' and 275 F. immediately cooling the milkby brlllinsthe container into contact with ycoldlklllid- '2. A process for sterilizing evaporated milk which comprises filling evaporated milk into a container, preheating the milk in the container to atemperature between about 160' and 190' F., thereafter rotating said container about its longitudinalaxiswlthsaidaxisinahorimntalposifluid at a temperature snmcient to raise the temperature ofthe milk from between 160 and 190*- `Etobetweenli" andZIS'Rinapcriodnot exceeding about 1% minutes and when said milk attalnsatemperaturebetweensboutmand 275 immediately cooling the milk by bringing the container into contact with cold liquid.

nom'rnuvnns.

nomi-n.110 w man 27 1915.

' `It is hereb" certifiedthat error appeasr'srn the printed specification ofthe above numbered patentlrequiring correction asfoll'one: Page 1, sec- I ond column, line 25, for "haz"l 'read -hae; page 5, second column, line 15 lfter the word 'between'I insert .'about'; line" 66, for' desirablez read undes1rab1e; yand that the said Letter-s Patent ahouldbe read with ibis correction lherein that the eamo-nay 'conform to the record` of the oase in eine Patent office.

signed and sealed this 5th day er June, l. n. '19h15.

`I (Seal) Leslie Frazer Acting Commissioner of Patents. 

